It applies in the field of antenna processing, where the signals originating from one or more emitters (sources) are received on a system of several sensors. The sources are received at different angles of incidence.
In an electromagnetic context, the sensors are antennas and the sources emit a polarized radioelectric signal. In an acoustic context the sensors are microphones and the sources are sound sources.
The sensors of the array receive the sources with a phase and an amplitude dependent on their angle of incidence as well as on the position of the antennas in terms of narrowband, plane wavefront and with no perturbations on the reception channels and the sensors of the array.
The antenna processing techniques currently known have the principal objective of utilizing spatial diversity. More particularly, the direction finding or locating of sources has the objective of estimating the angles of incidence of the emitters on the basis of an array of sensors.
In a nominal fashion, the direction finding procedures like MUSIC [1] assume that the wavefront is plane, that the sources are narrowband, point sources, with no polarization diversity, no coherent path and no disturbance of the response of the sensor array to a source. When one of these suppositions does not hold, the response of the array of sensors to a source no longer depends solely on the incidence but on other parameters such as the bandwidth, the coupling coefficients, the width of the diffusion cone or else the source-sensor distance.
The prior art describes various techniques making it possible to compensate for some of these disturbances. The estimation of the secondary parameters (parameters other than the incidence) is not envisaged in most techniques with the exception of reference [2] for polarization diversity. Techniques thus exist which adapt direction finding algorithms to diffuse sources [3][4][5]. For the wideband context, there exist focusing techniques [6][7] or spatio-frequency techniques [8][9][10][11]. For the techniques for compensating for the distortions of the response of the array the literature is very rich [12][13] etc.
In the prior art the techniques for compensating for the distortions of the response of the array of sensors process each of the disturbances in an isolated fashion without however taking account of several disturbances at one and the same time. Such techniques therefore turn out to be inadequate, in particular, in numerous acoustic applications where the wave is at one and the same time wideband and received as a curved wavefront. For radioelectric sources, it is possible to have an antenna array disturbed by coupling with polarization diversity waves and coherent paths.